Component comprising a microstructured functional element

ABSTRACT

A metallic cast component includes at least one microstructured functional element on a predefined surface area of the component with a relief-shaped structure sized in a micrometer range in at least one spatial direction for realizing a particular function. The functional element has at least one characteristic dimension of a length of less than 100 μm.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of prior filed copending U.S. applicationSer. No. 11/238,184, filed Sep. 28, 2005, the priority of which ishereby claimed under 35 U.S.C. §120 and which is continuation of priorfiled copending PCT International application no. PCT/DE2004/000638,filed Mar. 26, 2004, which designated the United States and on whichpriority is claimed under 35 U.S.C. §120 and which claims the priorityof German Patent Application, Serial No. 103 14 373.4, filed Mar. 28,2003, pursuant to 35 U.S.C. 119(a)-(d).

The content of U.S. application Ser. No. 11/238,184 is incorporatedherein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The invention relates to a primary shaping method for a component havingat least one microstructured functional element, which is configuredintentionally with a defined reliefed structure at a defined point onthe surface of the component in order to specifically fulfill a functionand which comprises, in at least one spatial direction, a characteristicdimension in the micrometer range, said component being shaped from asubstantially metallic material using a molding tool. As compared to acomponent having a purely macroscopic function, such a componentadditionally comprises a reliefed, microstructured and, as a resultthereof, functionalized surface.

Shaping methods substantially form the three-dimensional shape of acomponent without changing its mass. Primary shaping methods, which,from the liquid or ductile or from the granular or powdery aggregatestate (in the classification in accordance with DIN 8580)—create thefirst three-dimensional shape, and primary shaping methods, which changea three-dimensional shape in the solid aggregate state through pressure,tensile and compressive loads, bending or pushing loads (in theclassification in accordance with DIN 8580) are known.

In this context, the molding tool is the tool by means of which thethree-dimensional shape of the component is imposed. In the context ofthe shaping method, the material deposits in its respective aggregatestate on the surface of the molding tool—for example of a mold cavity ina casting method. A negative of a functional element formed on thesurface of the molding tool is thus directly formed in the functionalelement on the surface of the component that fits the mold. From thegreat number of known primary shaping methods forming thethree-dimensional shape of components from a substantially metallicmaterial, using a molding tool, casting, sintering and liquid-phasesintering will be mentioned in particular herein.

A microstructure is a reliefed surface structure comprising, in at leastone spatial direction, a characteristic dimension in the micrometerrange—meaning substantially of considerably less than 1 mm. Such acharacteristic dimension is for example the depth of an edge offsetdownward with respect to a surface or the width of a rib placed onto asurface.

Microstructures have been found to be advantageous in many respects.Microstructured surfaces are utilized for example in tribologicalapplications, from aero or fluid-dynamic point of views, because ofspecific visual properties, for controlling the wettability ornon-wettability with liquids and for promoting or preventing organicgrowth.

A functional element is an element that is intended to perform a definedfunction thanks to a defined shape. More specifically, a functionalelement is not an element that performs the defined function at afortuitous location on a component or by having a fortuitous shape.

A microstructured functional element accordingly is an element that isintentionally and selectively configured to have a defined structure ata defined point on the surface of a component and that has a dimensionin the micrometer range which is characteristic of the function.

A periodic or almost periodic arrangement of microstructured functionalelements is considered to be a microstructured surface texture, adefined detail of a surface having microstructured elements as thefunctional region or a functional element (itself composed of smallerfunctional elements).

Thanks to its reliefed structure in the region comprising the functionalelement, the surface of the component is either functionalized or hasits function optimized there. The flow guidance at the surface of aturbine bucket may for example be significantly improved by amicrostructured surface texture.

Beside the material and its microstructure, as well as the macroscopicshape, it is the surface that determines the properties of a component.On the one side, perfectly smooth surfaces have come to representtechnical perfection, on the other side, minute structures provide asurface with dirt- and water-repelling functions through what is knownas the “Lotus effect”, spectacle lenses can be provided with anadditionally antireflection coating applied to the surface thereof. Thefunctions of light reflection, flow resistance, heat transfer andfriction of a component's surface may also be selectively influenced bymicroscopic surface structures.

The manufacturing of large microstructured surfaces on plasticmaterials—at least on planar surfaces—is to be considered to be largelyknown: surface structures in the micrometer range are formed andreplicated, using the comparatively simple methods of soft lithographyunder normal atmosphere. The PDMS (polydimethyl siloxane) stamps used insoft lithography hereby form structures with characteristic dimensionsof less than 100 nm (H Schmid, B Michel, Macromolecules 33, 2000, p.3042). In the field of plastic materials, optical data carriersconstitute moreover an impressive example of a product with amicrostructured surface: CD-ROM disks, manufactured on a large scale byinjection molding, have structures of less than 1 μm, DVD havingstructures of even less than 500 nm. The production of a plurality ofother surface structures, including but not limited to, biomimeticstructures such as “shark skin” on polymers is already known.

On ceramic materials, surface structures in the micrometer range arealso reproduced neatly, as has been exemplified by a kind of slipcasting in structured PDMS stamps (U P Schönholzer et al.“Micropatterned Ceramics by Casting into Polymer Moulds” J. Amer. Soc.85 7, 2002, p. 1885). Also known is the manufacturing of structureshaving a size of as little as 10 nm by pressing into the molten surfaceof a silicon wafer a quartz disk patterned using electron beamlithography (S Y Chou, Ch Keimel, Jian Gu “Ultrafast and Direct Imprintof Nanostructures in Silicon”, Nature 417, 2002, p. 835).

Vapor deposited coatings on metallic components having a roughness inthe nanometer range are also known; these coatings however do not have ageometrically defined structure. On the other side, the function of ametallic surface can be influenced within narrow limits by selective,geometrically defined patterning on the microscopic scale using chemicaletching, micromachining or laser patterning. Structures geometricallydefined in the nanometer range can be produced on small surface portionsof a metallic component's surface using electron beam lithography.

FDA standardizes in detail indications as to the microstructure of thesurface for approving a modified metallic surface of orthopedicimplants: the thickness of a coating, the pore diameter, the shape anddimensions of the material between the pores and the volume percent ofthe voids must be determined in complex test series through theirstatistical average and limit values as well as through their standarddeviation (U.S. Food and Drug Administration: Guidance Document forTesting Orthopedic Implants with Modified Metallic Surfaces ApposingBone or Bone Cement. February 2000,http://www.fda.gov/cdrh/ode/827.html.

As compared with plastic components with microstructured surfaces, theproduction of metallic microstructured functional elements on metalliccomponents manufactured using primary shaping methods is interestingfrom many point of views because they are less prone to wear and exhibithigher hardness and because they may additionally be utilized at highertemperatures. However, the known methods for modifying the surfacestructure can be utilized for some few special applications only if theyare to be economically efficient, this being due on the one side totheir complexity and on the other side to the demands placed on testingand documentation because of the statistical distribution of theproperties.

The document DE 101 54 756 C1 discloses a primary shaping method, usinga molding tool in the surface of which microscopic cavities are formedby anodic oxidation, directly and without a model—meaning so as to bestatistically distributed. The document EP 0 838 286 A1 discloses aninvestment casting method using a wax model on the surface of whichmolten wax is sprinkled to form a microporous surface structure, whichagain is statistically distributed. The document DE 38 31 129 A1discloses a method for manufacturing a casting mold on the basis of athermally sensitive model such as textiles, plastic material, wood orleather, with the surface structure of the model being reproduced in thecasting mold. The methods disclosed in these documents provide forstatistically distributed surface structures but not for a definedreliefed microstructured functional element at a defined point on thesurface of the component for selectively performing a function.

In the wider context of the invention, there is known from U.S. Pat. No.6,511,622 B1 to use a wax “filled” with particles for manufacturing awax model which in turn is used for investment casting in order tominimize the formation of microscopic defects in the surface of the waxmodel. The document DE 43 07 869 A1 discloses a primary shaping methodfor manufacturing a microscopic body as it is utilized in precisionengineering, micromechanics, microoptics and microelectronics; it doesnot disclose the formation of a microstructured functional element on amacroscopic component, though.

SUMMARY OF THE INVENTION

It is the object of the invention to provide method approaches, toolsand means that open new application fields for primary shaping methodsfor manufacturing microstructured surfaces on substantially metalliccomponents and to simplify and speed-up these methods and means morespecifically with regard to large-scale production and utilization.

In view of the known primary shaping methods, the object is solved, inaccordance with the invention, by having at least one functional elementshaped in a negative copy thereof that is formed in the surface of themolding tool.

A primary shaping method of the invention permits, concurrently with thepatterning of the macroscopic, three-dimensional shape of a component,the manufacturing of the microstructured functional element on thesurface thereof. As compared to the known primary shaping methods withsubsequent machining of the surface, one working step can be eliminatedin the manufacturing of a component having a microstructured functionalelement as a result thereof.

As compared to the known methods for manufacturing surface structures inthe micrometer range on a metallic component, primary shaping methods ofthe invention can be carried out at considerably lower costs on the oneside. On the other side, they allow for the first time the economicallyefficient manufacturing of large and/or curved surfaces provided withmicrostructures.

As compared to plastic surfaces, components with such defined structuredmetallic surfaces are characterized by higher surface hardness and, as aresult thereof, by higher mechanical strength, reduced wear and longerlife, by the fact that they may be utilized at higher temperatures andexhibit improved electrical and thermal conductivity.

BRIEF DESCRIPTION OF THE DRAWING

None

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The primary shaping method of the invention may be utilized toparticular advantage if the component is shaped by solidification of aliquid metal in a cavity of the molding tool. Such primary liquid phaseshaping methods allow for the one-step manufacturing of components ofalmost any complexity having dimensions of between some few millimetersto several meters. In primary shaping methods of the invention, detailsin the microstructure range can be produced in the surface of thecomponent in one and the same work step.

To carry out such a primary liquid phase shaping method of theinvention, the liquid metal is preferably poured into the molding tool.Alternatively, the metal may also be introduced into the molding toolusing sintering or liquid phase sintering methods and also in granularor powdery solid state to be liquefied by heating in the molding tool.In the context of thixoforming methods, the metal may also be introducedinto the molding tool in the thixothropic, meaning in the plasticallyductile state.

A “substantially metallic material” is understood to also refer to acomposite material having a metallic matrix and for example ceramic—thatis inorganic, nonmetallic—grains or fibers made from silicates,carbides, nitrides, for example hard materials such as tungsten carbide.

In the context of a primary liquid phase shaping method, the moldingtool's cavity may be provided before filling with a thin metal layerusing current methods such as PVD, CVD, MOCVD, with the coatingthickness ranging from a few atomic layers to some micrometers. Thispermits ensuring that even very fine structures in the surface of thecavity be optimally wetted by the molten metal. The molding tool maymore specifically be coated with the same metallic material with whichthe component will then be cast in the molding tool.

In the context of a primary shaping method, the molding tool, in aprimary shaping method, may more specifically be formed from a model.Such type primary shaping methods of the invention more specificallyinclude methods using what are referred to as “disposable molds” such asinvestment casting and sand casting. Investment casting is a currentmethod for producing filigree structures in metallic components. Ametallic permanent mold—which is referred to as a “die”—can bemanufactured in the context of a primary shaping method of the inventionsuch as by electric discharge machining or by the investment castingmethod of the invention. Such type casting methods of the invention morespecifically allow for repeated use of the same model and, as a resultthereof, for economically efficient series production of componentshaving microstructured functional elements.

Chemical vapor deposition of a thin metal or ceramic layer onto thestructured model or the structured mold has been found appropriate toreplicate finest structures. The methods used here are for examplemetal-organic CVD methods in which the metal deposits on the model atlow temperatures. Alternatively, the coating material can also bevaporized by bombarding it with a solid body by means of a laser(sputtering).

Alternatively, in the context of a primary shaping method of theinvention, permanent molding tools can be assembled from assembly partsor manufactured by metal removing or electric discharge machiningmethods. In special applications—for example in the context of rapidprototyping—a molding tool may also be manufactured by layeredmanufacturing methods.

In the context of a primary shaping method of the invention, thefunctional element is preferably formed on the model and then replicatedfrom the model in the moulding tool. If the same model is used severaltimes, the primary shaping method is simplified and the economicefficiency of the primary shaping method increased with regard to themanufacturing of the negative of the functional element on molding toolsthat have been produced in series.

Alternatively, the functional element may be placed in the surface ofthe molding tool in the context of a primary shaping method of theinvention by a separately performed reshaping step such as by stamping,by metal removing or electric discharge micromachining or by applying oradding prefabricated standard parts.

On a ceramic shell mold for an investment casting method of theinvention, the negative of the functional element can be mounted eitherin the surface of the ceramic produced by dipping it as described or inthe surface of a black wash applied subsequently.

In the context of a primary shaping method of the invention, the modelcan be removed from the replicated molding tool by melting, vaporizing,dissolving or by any other means. Such primary shaping methods of theinvention using what is referred to as a “disposable model”, which isused but once, again include investment casting methods. A wax orplastic model is therefore dipped repeatedly in a ceramic slip toconstruct, layer by layer, the ceramic shell mold. Once the molding toolis completed, the model is removed by melting it away or burning it out.In “lost foam” sand casting, a sand mold is constructed about a foammodel, said foam model evaporating when the liquid metallic material ispoured into the completed molding tool.

In the context of a primary shaping method of the invention, the modelmay more specifically be replicated from a primary mold in a primaryshaping method. A wax model for an investment casting process of theinvention may for example be replicated from a metallic primary mold.This makes economically efficient series production of components withmicrostructured functional elements possible using a primary shapingmethod of the invention making use of a “disposable model”.

Alternatively, the model can also be assembled from assembly parts ormanufactured by metal removing or electric discharge machining methodsin the context of a primary shaping method of the invention. In specialapplications—again in the context of rapid prototyping—the manufacturingof a model using layered manufacturing methods is also possible.

In the context of a primary shaping method of the invention, thenegative of the functional element is preferably formed in the primarymold to be replicated from the primary mold to the model. If the sameprimary mold is used several times, the primary shaping method issimplified and the economic efficiency of the primary shaping methodincreased, also with respect to the manufacturing of the functionalelement on models produced in series.

Alternatively, the functional element can also be placed in the surfaceof the model in the context of a primary shaping method of the inventionby a separately performed reshaping step such as by stamping, by metalremoving or electric discharge micromachining or by applying or addingprefabricated standard parts.

In the context of a primary shaping method of the invention, the primarymold may more specifically be replicated from a primary model in aprimary shaping method. A primary mold for an investment casting processof the invention may for example be replicated from a primary modelbuilt for example in a rapid prototyping stereolithography process. Thispermits to significantly shorten the time required for series productionof numerically optimized components having microstructured functionalelements to begin, using primary shaping methods of the invention makinguse of a “disposable model”.

Alternatively, the primary mold may again be assembled from assemblyparts or manufactured by metal removing or electric discharge machiningmethods in the context of a primary shaping method of the invention. Inprinciple, it is also possible to manufacture a primary mold usinglayered manufacturing methods.

In the context of a primary shaping method of the invention, thefunctional element is preferably formed on the primary model and isreplicated from the primary model onto the primary mold. If the sameprimary model is used several times, the primary shaping method issimplified and the economic efficiency of the primary shaping methodincreased, also with respect to the manufacturing of the negative of thefunctional element on primary molds produced in series.

Alternatively, the negative of the functional element can also be placedin the surface of the primary mold in the context of a primary shapingmethod of the invention by a separately performed reshaping step such asby stamping, by metal removing or electric discharge micromachining orby applying or adding prefabricated standard parts.

In the context of a primary shaping method of the invention, thefunctional element formed more specifically is a freeform that projectsfrom the surface of the component. A freeform may for example reproducethe shape of a shark's scale so that a plurality of such functionalelements will provide the surface of a component with particularlyadvantageous properties in terms of fluid flow.

The functional element preferably has a characteristic dimension with alength of less than 500 μm, more specifically of less than 300 μm. It isparticularly preferred if the length is less than 100 μm, or rather lessthan 10 μm. Tests showed that structures in the submicrometer range ofeven less than 100 nm may also be replicated.

The characteristic dimension of the functional element can be in theplane of the component's surface. The functional element may for examplebe a 10 mm deep notch in the surface of the component. Thecharacteristic dimension may also be perpendicular to a component'ssurface. The functional element may for example be a cone protruding 50μm from the surface of the component. With microstructured surfacetextures in particular, a (mathematically averaged) area can be regardedas the surface and the spacing between various neighboring functionalelements or the local distance of the envelope of the relief, as thecharacteristic dimension.

The functional element may more specifically be a step, with thecharacteristic dimension being the height of the step with respect tothe surface of the component. The step—meaning a substantially linearprotrusion projecting from the surface of the component—virtuallyconstitutes in the nanostructure range the elementary shape of afunctional element. Unidimensional, meaning really spot-likeprotrusions, cannot be produced in reality.

Further, in the context of a primary shaping method of the invention, aplurality of functional elements is preferably formed on the component.Elementary functional elements may for example be arranged in the formof a Fresnel lens so as to be optically active—at need in the UVrange—or they may constitute the contours of a brand name or logotype toidentify the manufacturer. By combining functional elements in themicrostructure range, the material can be superficially reinforced—atneed as a function of the direction—and tribologic or fluid dynamicaleffects can be achieved.

In the context of a primary shaping method of the invention, a surfacetextured functional region is further preferably shaped from functionalelements that are periodically arranged in the surface of the component.The functional elements arranged in the component's surface may also bearranged in a graded periodical manner, meaning in such a manner that atleast one characteristic dimension, the height with respect to thesurface, changes the relative position or the spacing betweenneighboring functional elements over the surface of the component.

In the context of such a primary shaping method of the invention, it isparticularly preferred if a functional region comprises a biomimeticsurface structure. A plurality of surface effects occurring in natureand originating in the microstructure range is known. Examples includeshark skin, sand skink, lotus leaves and garden cress.

The object is further solved in accordance with the invention by amolding tool for a component having a microstructured functionalelement, said component being shapeable from a substantially metallicmaterial by means of the molding tool and a surface of the molding toolcomprising a negative of the functional elements by means of which thefunctional element may be formed. The primary shaping method describedherein above may be carried out using such a molding tool of theinvention.

The molding tool of the invention may more specifically be a disposableceramic mold. The molding tool of the invention may more particularlyinclude a core comprising the negative of the functional element. Amicrostructured functional element may also be formed in a cavity of thecomponent by means of such a molding tool of the invention. The negativeof the functional element may in turn be installed on a core of theinvention, either in the surface thereof or in the surface of a blackwash applied subsequently.

The object is further solved in accordance with the invention by a corefor a component having a microstructured functional element, saidcomponent being adapted to be formed from a substantially metallicmaterial in a cavity of a molding tool including the core, said corecomprising a negative of the functional element that may be replicatedfrom the core onto the component. The primary shaping method describedherein above may be carried out by means of such a core of theinvention.

The object is further solved in accordance with the invention by a corebox for a component having a microstructured functional element, saidcomponent being adapted to be formed from a substantially metallicmaterial in a cavity of a molding tool including a core that is adaptedto be formed in the core box, said core box comprising the functionalelement that may be replicated from the core box onto the core and fromthe core onto the component. The primary shaping method described hereinabove may also be carried out by means of such a core of the invention.

The object is further also solved in accordance with the invention by amodel for a component having a microstructured functional element, amolding tool being adapted to be replicated from the model in a primaryshaping method, said component being adapted to be formed from asubstantially metallic material in a cavity of the molding tool and themodel comprising the functional element that may be replicated from themodel onto the molding tool and from the molding tool onto thecomponent. The primary shaping method described herein above may becarried out by means of such a model of the invention.

The object is further also solved in accordance with the invention by aprimary mold for a component having a microstructured functionalelement, a model being adapted to be replicated from the primary moldand a molding tool, from the model respectively using a primary shapingmethod, with the component being adapted to be formed from asubstantially metallic material in a cavity of the molding tool, saidprimary mold comprising a negative of the functional element that may bereplicated from the primary mold onto the model, from the model onto themolding tool and from the molding tool onto the component. The primaryshaping method described herein above may be carried out by means ofsuch a primary mold of the invention.

Such a primary mold of the invention may more specifically be made froman elastomer. The primary mold may for example be replicated in PDMSfrom a primary model.

Finally, the object is solved in accordance with the invention by aprimary model for a component having a microstructured functionalelement, a primary mold being adapted to be replicated from the primarymodel, a model, from the primary mold and a molding tool, from themodel, respectively using a primary shaping method, with the componentbeing adapted to be shaped from a substantially metallic material in acavity of the molding tool, with the primary model comprising thefunctional element, said functional element being adapted to bereplicated from the primary model onto the primary mold, from theprimary mold onto the model, from the model onto the molding tool andfrom the molding tool onto the component. The primary shaping methoddescribed herein above may also be carried out by means of such aprimary mold of the invention.

Exemplary Embodiments

To manufacture a turbine bucket from directionally solidifiednickel-base superalloy SC16 having an undulated surface structure, adecorative glass foil usual in commerce and having an undulated surfacestructure is glued on a metallic turbine bucket model used as theprimary model, said turbine bucket model being then replicated in PDMS.The decorative glass foil is 120 μm thick. The wax model is manufacturedin the thus achieved primary mold, and as a result thereof, the ceramicshell mold that will be used as the molding tool, by dipping it into aslip and coating it with sand. The turbine bucket is cast using theprocess generally known as the Bridgman casting process.

To manufacture a casting from an aluminum alloy with visible replicationof a logotype, this logotype is printed on a foil by means of a laserprinter. The lateral structure size of the toner applied onto the foilis about 200 μm, the thickness of the toner layer, about 10 μm. The foilis glued into a permanent molding tool for wax models. In the permanentmolding tool, the wax model is manufactured using the full mold process(Shaw process). The aluminum casting is cast using the process generallyknown as the differential pressure casting process.

To manufacture a test body with finest structures, a primary model inthe form of a quartz plate is manufactured using generally knownelectron beam lithographic processes. This quartz plate has linearstructures spaced 4 μm apart and having a width of 4 μm as well and adepth of 200 nm. The primary model is replicated in PDMS to form theprimary mold; the wax model from which the shell mold may be produced ismanufactured in the primary mold.

For manufacturing simple structured surfaces, it is possible to usecommercially available primary molds that are made using for exampleconventional photolithography. The length spectrum obtainable withsimple photolithography includes structures of up to a few micrometers.Primary molds may be used for smaller structures that are for examplemanufactured using nanoimprint lithography. The structures that can bereplicated using this technique are only about 10 nm in size andconstitute the limit of present lithography.

As a rule—and in particular if the structures are very fine—surfacesmanufactured by lithography may only be produced on planar substratesand with areas in the range of one square centimeter.

Larger microstructured surfaces are produced by modular combinationeither of these primary models manufactured by lithography or, inaccordance with the invention, of models or molding tools replicatedfrom these primary models. Wax models or the primary molds used tomanufacture these are reshaped to replicate planar microstructures onthree-dimensionally curved simple shape bodies such as half shells,tubes, cylinders, cones and cuboids or on complex cast components suchas turbine buckets.

As contrasted to the standard methods for manufacturing primary moldsfor wax models, so-called wax matrices, in investment casting, jewelrycasting or prototype casting, which rely on embedding the molds in hotvulcanisate molding tools under pressure at temperatures of 150° C. andrequire the use of a release agent, the primary model is, in accordancewith the invention, embedded without pressure in an elastomer in orderto manufacture the primary mold. To replicate the wax models, theprimary mold is evacuated before it is filled with wax in order toprevent microscopic gas bubbles to form in the wax model. The wax isforced under pressure into the primary mold to fill it completely and tothus achieve good replication.

The ceramic molding tools having microstructures are manufactured usingknown investment casting methods. To increase replication accuracy, theslips and/or embedding materials used are modified by adding ceramicnanopowder. The directional solidification of the metal alloy in theBridgman process ensures continuous supply and makes it possible toproduce components without grain boundary.

Methods of the invention also permit to manufacture components havingmicrostructured functional elements which serve as reshaping tools andtransfer the surface structure, in a reshaping procedure, onto anothercomponent or semi-finished product such as rollers, embossing rollers,roller pairs, presses, embossing tools and deep-draw molds.

Methods of the invention further enable components havingmicrostructured functional elements to be produced for

-   -   aerodynamic applications such as turbine buckets for aircraft        turbines or stationary turbines, turbocharger wheels, valves,        exhaust manifolds, intake tubes, nozzles, fans and bullets,    -   fluid dynamic applications such as ship's propellers, nozzles,        pump housings and impellers, screw conveyors, torpedoes and        microreactors,    -   medical applications such as heart valves with improved flow        characteristics and reduced calcium deposition, implants or        dental prostheses with improved bonding and surgical        instruments,    -   tribological applications such as bearing blocks, cylinder and        piston units, runners such as for skates, electric irons, screw        conveyors and brake disks,    -   use of the abrasive effect of the surface structure of the        casting such as for filing and milling,    -   surface-specific applications such as catalysts, heat        exchangers, cooling elements and microfluidic components,    -   wetting specific applications such as car wheels and bicycles,        dies for casting, frying pans, cooking pots and microreactors,    -   micromechanical applications such as the precise positioning of        individual fibers in glass fiber bundles,    -   optical applications such as antireflection surfaces,        antireflection coatings and molds for lenses,    -   reinforcing thin walls,    -   aesthetic applications such as jewelry like structured metal        tapes and visual surface design in general.

1. A metallic cast component, comprising at least one microstructuredfunctional element on a predefined surface area of the component with arelief-shaped structure sized in a micrometer range in at least onespatial direction for realizing a particular function, said functionalelement having at least one characteristic dimension of a length of lessthan 100 μm.
 2. The component of claim 1, wherein the functional elementis a free formed area.
 3. The component of claim 1, wherein thecharacteristic dimension is smaller than 10 μm.
 4. The component ofclaim 1, comprising a plurality of said functional element.
 5. Thecomponent of claim 4, comprising at least one functional region formedfrom functional elements periodically arranged in a surface of thecomponent.
 6. The component of claim 5, wherein the functional regionincludes a biomimetic surface structure.
 7. The component of claim 1,wherein the relief-shaped structure is formed in the absence of anyfurther refinishing step.
 8. A component with at least onemicrostructured functional element, said component being produced by aninvestment casting method comprising the steps of: producing amicrostructure at a predefined area on a cavity-confronting surface of amolding tool; introducing a substantially liquid metallic material inthe cavity of the molding tool; and molding a component in the cavity ofthe molding tool, thereby reproducing on an outside surface of thecomponent a positive of the microstructure to form a microstructuredfunctional element so as to provide the component at a defined area witha relief-shaped structure sized in a micrometer range in at least onespatial direction for realizing a particular function, wherein thefunctional element has at least one characteristic dimension, with thecharacteristic dimension being a length of less than 100 μm.
 9. Thecomponent of claim 8, wherein the functional element is a free formedarea.
 10. The component of claim 8, wherein the characteristic dimensionis smaller than 10 μm.
 11. The component of claim 8, comprising aplurality of said functional element.
 12. The component of claim 11,comprising at least one functional region formed from functionalelements periodically arranged in a surface of the component.
 13. Thecomponent of claim 12, wherein the functional region includes abiomimetic surface structure.
 14. The component of claim 8, wherein therelief-shaped structure is formed in the absence of any furtherrefinishing step.